/*================================================================
*   Copyright (C) 2019 Guangzhou Firefly Ltd. All rights reserved.
*   
*   文件名称：get_cube_root.c
*   创 建 者：luhuadong
*   创建日期：2020年07月08日
*   描    述：求解立方根
*
================================================================*/


#include <stdio.h>

static double getCubeRoot2(double input)
{

}

static double getCubeRoot(double start, double end, double input)
{
    double mid = (end+start)/2;
    if(mid*mid*mid-input<0.0000001 && mid*mid*mid-input>-0.00000001)
        return mid;
    if(mid*mid*mid-input>0)
        return getCubeRoot(start,mid,input);
    return getCubeRoot(mid,end,input);
}

int main(void)
{
	double a;
	scanf("%lf", &a);

	printf("%.1f\n", getCubeRoot(0, a, a));
	return 0;
}